PDAAM/PU同步互穿网络聚合物的力学性能

利用互穿聚合物网络技术(IPN),将双丙酮丙烯酰胺(DAAM)用于PU胶粘剂的改性.研究了组分比、引发剂用量、固化参数对PDAAM/PU IPN力学性能的影响.结果表明,PDAAM可以提高PU的力学性能.当DAAM的质量分数在40%时,拉伸强度及断裂伸长率都达到最大值.     

IMS早期媒体建立中多实体媒体协商解决方案

对IMS建立早期媒体的信令流程进行了研究,分析了具有MRS(媒体资源服务器)的IMS系统建立早期媒体的方案.并给出了使用信令流程和分类规则解决网关模式下多实体建立早期媒体过程中出现的offer/answer不匹配问题的方案.     

75t循环流化床锅炉烟气超洁净排放技术的研究与应用

以纯煤泥75t中温中压循环流化床锅炉和国家脱硝、脱硫等更严格环保政策为工程背景,通过对分离器、回料器优化、增加水冷受热面积、流化床布风板和优化一二次风以及优化尾部受热面来降低锅炉烟气,从而达到降低初始排放浓度;通过脱硫除尘一体化装置实现超洁净排放。结合现场实际情况消除旋风分离器中易结灰垢,实现了纯煤泥75t中温中压循环流化床锅炉稳定生产和超洁净排放。     

制浆麦渣颗粒燃料的成型特点及燃烧特性研究

以制浆造纸企业备料工段的麦草废渣和制浆废液为原料,利用液压成型机制备麦渣颗粒燃料,探究其成型特点和燃烧特性.研究了麦渣粒径和废液添加量对麦渣颗粒燃料成型效果的影响,分析了燃料颗粒灰分、挥发分、固定碳及发热量的变化规律,得出了麦渣颗粒燃料的较优制备条件.结果表明,随着麦渣粒径减小,麦渣颗粒燃料成型密度逐渐增大,当麦渣粒径...     

制备参数对聚醚砜/非织造布复合膜空气过滤性能的影响

聚醚砜(PES)是一种综合性能优良的聚合物成膜材料,熔喷非织造布具有良好的过滤效能并广泛应用于空气的过滤.聚醚砜/非织造布复合膜是以PES膜材、致孔剂聚乙烯吡络烷酮(PVP)和溶剂N,N-二甲基乙酰胺(DMAc)作为铸膜液并涂覆在熔喷非织造布上,然后转移至凝固浴中成膜.通过控制铸膜液组分的不同比例、凝固浴温度和第一凝固...     

基于UML的C3I系统软件建模

UML是一种通过面向对象分析确定由类图和行为图表述的逻辑体系结构和通过面向对象设计确定由构件图和配置图表述的物理体系结构的方法,目前已经成为面向对象分析与设计建模事实上的标准;首先介绍了UML技术及其在开发应用程序中的一般框架,并以此为依据,使用UML结合光电干扰武器系统C3I的建模应用实例对其进行了具体论述。     

Mechanical and thermal properties of light weight boron-mullite Al5BO9

Al₅BO₉ is a promising thermal sealing material for hypersonic vehicles due to its low density, theoretically predicted low shear modulus, and low thermal conductivity. However, experimental investigations on the mechanical and thermal properties of bulk Al₅BO₉ have not been carried out. Herein, we report the mechanical and thermal properties of bulk Al₅BO₉ prepared by spark plasma sintering of solid-state reaction synthesized Al₅BO₉ powders. The bulk (B), shear (G), and Young's (E) moduli are 148 GPa, 85 GPa, and 214 GPa, respectively, which are close to the theoretical values. The Pugh's ratio G/B is 0.574, indicating its intrinsic damage tolerance, which is also revealed by Hertzian contact test. The Vickers hardness (H_v) is 10.8 GPa, being lower than mullite. The flexural strength, compressive strength, and fracture toughness are, respectively, 277 ± 35 MPa, 814 ± 75 MPa, and 2.4 ± 0.3 MPa·m^1/2, which are close to those of mullite. Al₅BO₉ has anisotropic coefficient of thermal expansion (CTE) in three crystallographic directions, ie α_a = (4.40 ± 0.21) × 10⁻⁶ K⁻¹, α_b = (7.11 ± 0.18) × 10⁻⁶ K⁻¹, α_c = (6.70 ± 0.29) × 10⁻⁶ K⁻¹ from Debye temperature to 1473 K, which are underpinned by its structural feature, ie lower α_a is resulted from the edge-shared AlO₆ octahedron chains along the [100] direction. The average CTE is (6.05 ± 0.06) × 10⁻⁶ K⁻¹. The thermal conductivity declines with temperature as κ = 1336.39/T + 1.97, consisting with predicted trend from Slack's model. The low thermal conductivity and low density guarantee Al₅BO₉ a promising candidate as ceramic wafer in the seal structure for hypersonic vehicles.     

Novel thermal-sensitive properties of NBT-BZT composite ceramics for high-temperature NTC thermistors

We found for the first time that (1 − x) Na_0.5Bi_0.5TiO₃-xBiZn_0.5Ti_0.5O₃ (NBT–BZT) composite ceramics showed negative temperature coefficient (NTC) at a high temperature. The NBT–BZT nanopowders were successfully prepared by Pechini method. Their ceramics were sintered at 1100°C. The NBT–BZT ceramic exhibited a good linear relationship between logarithm of electrical resistivity (Inρ) and reciprocal of absolute temperature (1000/T) at 250°C–1050°C. The obtained ρ₆₀₀, ρ₉₀₀, and B_600/900 constants of the NBT–ZBT NTC thermistors are approximately 5.92 × 10⁶ to 3.01 × 10⁴ Ω cm, 7.03 × 10³ to 7.60 × 10² Ω cm and 2.3 × 10⁴-1.3 × 10⁴ K, respectively. The electrical characteristics can be tuned to the desired value by changing the Na_0.5Bi_0.5TiO₃ content in the compound. The electrical conductivity in these compounds is due to the electron jumps between Ti³⁺ and Ti⁴⁺ and oxygen-ion conductivity. Results demonstrate a tremendous potential of the studied system for perovskite materials with NTC performance.     

Strategy to design high performance TiB2-based materials: Strengthen grain boundaries by solid solute segregation

TiB₂ exhibits a unique combination of excellent properties that make it promising candidate for applications in extreme environments, where retention of strength at high temperatures is essential. Tailoring grain boundary properties by segregation is believed a prominent way to design high-temperature performance of ceramics. In this work, segregation tendencies of solute elements, including Sc, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, in TiB₂ grain boundaries and the strengthening/weakening effects induced by segregations are investigated by first-principles calculations. The results reveal that small atoms tend to segregate to grain boundary sites with local compression strains, while large atoms prefer grain boundary sites with local expansion strains. Deteriorated grain boundary strength is usually caused by additional expansion strain induced by segregation, while improved grain boundary strength results from either enhanced local bonding induced by segregation of small atoms or increased fracture strain due to segregation of large atoms. Cr and V, especially Cr, exhibit strong segregation tendency and improvement on grain boundary strength, which provides useful guidelines for the design of high performance TiB₂-based materials.     

电子延迟器控制的三级震源叠加技术

在厚黄土层地表区地震数据采集中,多级延迟叠加震源方法具有先进性,但现今采用机械武打击片或螺旋式导爆管控制震源延时爆炸的方法,存在延时精度低、结构复杂、加工成本高及效率低等问题.使用电子雷管虽可较精准实现多级震源延迟叠加,但由于费用过高而难以大规模使用.文中介绍一种电子延迟技术控制多级震源叠加的方法,并详述地表控制电路(...